French physicist Claude Cohen-Tannoudji studied under Alfred Kastler, and building on the work of Steven Chu and William D. Phillips, refined the process of optical cooling and developed laser traps to isolate single atoms through a process called Sisyphus cooling. Also called polarization gradient cooling, this process takes advantage of the phenomenon by which atoms in certain states "climb uphill", or are optically pumped into another state, which effectively reduces the kinetic energy of the bombarded atoms and brings sub-Doppler temperatures.

Cohen-Tannoudji's work has allowed increasingly detailed study of atomic structure, and is seen as a bridge between classical and quantum physics. With Chu and Phillips, he won the 1997 Nobel Prize for Physics, and he has also studied Bose-Einstein condensation, photon correlations, quantum electrodynamics, quantum interference effects, radiative forces and corrections, and resonance fluorescence.